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Programming Challenge redislabs-training#3
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@ThiernoAmirouDiallo
ThiernoAmirouDiallo committed Nov 14, 2022
1 parent c82b370 commit cf0b231
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Showing 2 changed files with 88 additions and 77 deletions.
1 change: 1 addition & 0 deletions src/main/java/com/redislabs/university/RU102J/api/SiteStats.java
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Expand Up @@ -12,6 +12,7 @@ public class SiteStats {
private Double minWhGenerated;
private Double maxCapacity;


/* These field names will be used by multiple classes, so we define
them here to abide by DRY (don't repeat yourself). */
public final static String reportingTimeField = "lastReportingTime";
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164 changes: 87 additions & 77 deletions src/main/java/com/redislabs/university/RU102J/dao/SiteStatsDaoRedisImpl.java
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Expand Up @@ -3,88 +3,98 @@
import com.redislabs.university.RU102J.api.MeterReading;
import com.redislabs.university.RU102J.api.SiteStats;
import com.redislabs.university.RU102J.script.CompareAndUpdateScript;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;

import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.util.Map;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.Transaction;

public class SiteStatsDaoRedisImpl implements SiteStatsDao {

private final int weekSeconds = 60 * 60 * 24 * 7;
private final JedisPool jedisPool;
private final CompareAndUpdateScript compareAndUpdateScript;

public SiteStatsDaoRedisImpl(JedisPool jedisPool) {
this.jedisPool = jedisPool;
this.compareAndUpdateScript = new CompareAndUpdateScript(jedisPool);
}

// Returns the site stats for the current day
@Override
public SiteStats findById(long siteId) {
return findById(siteId, ZonedDateTime.now());
}

@Override
public SiteStats findById(long siteId, ZonedDateTime day) {
try (Jedis jedis = jedisPool.getResource()) {
String key = RedisSchema.getSiteStatsKey(siteId, day);
Map<String, String> fields = jedis.hgetAll(key);
if (fields == null || fields.isEmpty()) {
return null;
}
return new SiteStats(fields);
}
}

@Override
public void update(MeterReading reading) {
try (Jedis jedis = jedisPool.getResource()) {
Long siteId = reading.getSiteId();
ZonedDateTime day = reading.getDateTime();
String key = RedisSchema.getSiteStatsKey(siteId, day);

updateBasic(jedis, key, reading);
}
}

// A naive implementation of update. This implementation has
// potential race conditions and makes several round trips to Redis.
private void updateBasic(Jedis jedis, String key, MeterReading reading) {
String reportingTime = ZonedDateTime.now(ZoneOffset.UTC).toString();
jedis.hset(key, SiteStats.reportingTimeField, reportingTime);
jedis.hincrBy(key, SiteStats.countField, 1);
jedis.expire(key, weekSeconds);

String maxWh = jedis.hget(key, SiteStats.maxWhField);
if (maxWh == null || reading.getWhGenerated() > Double.valueOf(maxWh)) {
jedis.hset(key, SiteStats.maxWhField,
String.valueOf(reading.getWhGenerated()));
}

String minWh = jedis.hget(key, SiteStats.minWhField);
if (minWh == null || reading.getWhGenerated() < Double.valueOf(minWh)) {
jedis.hset(key, SiteStats.minWhField,
String.valueOf(reading.getWhGenerated()));
}

String maxCapacity = jedis.hget(key, SiteStats.maxCapacityField);
if (maxCapacity == null || getCurrentCapacity(reading) > Double.valueOf(maxCapacity)) {
jedis.hset(key, SiteStats.maxCapacityField,
String.valueOf(getCurrentCapacity(reading)));
}
}

// Challenge #3
private void updateOptimized(Jedis jedis, String key, MeterReading reading) {
// START Challenge #3
// END Challenge #3
}

private Double getCurrentCapacity(MeterReading reading) {
return reading.getWhGenerated() - reading.getWhUsed();
}
private final int weekSeconds = 60 * 60 * 24 * 7;
private final JedisPool jedisPool;
private final CompareAndUpdateScript compareAndUpdateScript;

public SiteStatsDaoRedisImpl( JedisPool jedisPool ) {
this.jedisPool = jedisPool;
this.compareAndUpdateScript = new CompareAndUpdateScript( jedisPool );
}

// Returns the site stats for the current day
@Override
public SiteStats findById( long siteId ) {
return findById( siteId, ZonedDateTime.now() );
}

@Override
public SiteStats findById( long siteId, ZonedDateTime day ) {
try ( Jedis jedis = jedisPool.getResource() ) {
String key = RedisSchema.getSiteStatsKey( siteId, day );
Map<String, String> fields = jedis.hgetAll( key );
if ( fields == null || fields.isEmpty() ) {
return null;
}
return new SiteStats( fields );
}
}

@Override
public void update( MeterReading reading ) {
try ( Jedis jedis = jedisPool.getResource() ) {
Long siteId = reading.getSiteId();
ZonedDateTime day = reading.getDateTime();
String key = RedisSchema.getSiteStatsKey( siteId, day );

updateOptimized( jedis, key, reading );
}
}

// A naive implementation of update. This implementation has
// potential race conditions and makes several round trips to Redis.
private void updateBasic( Jedis jedis, String key, MeterReading reading ) {
String reportingTime = ZonedDateTime.now( ZoneOffset.UTC ).toString();
jedis.hset( key, SiteStats.reportingTimeField, reportingTime );
jedis.hincrBy( key, SiteStats.countField, 1 );
jedis.expire( key, weekSeconds );

String maxWh = jedis.hget( key, SiteStats.maxWhField );
if ( maxWh == null || reading.getWhGenerated() > Double.valueOf( maxWh ) ) {
jedis.hset( key, SiteStats.maxWhField, String.valueOf( reading.getWhGenerated() ) );
}

String minWh = jedis.hget( key, SiteStats.minWhField );
if ( minWh == null || reading.getWhGenerated() < Double.valueOf( minWh ) ) {
jedis.hset( key, SiteStats.minWhField, String.valueOf( reading.getWhGenerated() ) );
}

String maxCapacity = jedis.hget( key, SiteStats.maxCapacityField );
if ( maxCapacity == null || getCurrentCapacity( reading ) > Double.valueOf( maxCapacity ) ) {
jedis.hset( key, SiteStats.maxCapacityField, String.valueOf( getCurrentCapacity( reading ) ) );
}
}

// Challenge #3
private void updateOptimized( Jedis jedis, String key, MeterReading reading ) {
String reportingTime = ZonedDateTime.now( ZoneOffset.UTC ).toString();

jedis.hset( key, SiteStats.reportingTimeField, reportingTime );
jedis.hincrBy( key, SiteStats.countField, 1 );
jedis.expire( key, weekSeconds );

Transaction transaction = jedis.multi();

compareAndUpdateScript.updateIfGreater( transaction, key, SiteStats.maxWhField, reading.getWhGenerated() );
compareAndUpdateScript.updateIfLess( transaction, key, SiteStats.minWhField, reading.getWhGenerated() );
compareAndUpdateScript.updateIfGreater( transaction, key, SiteStats.maxCapacityField, getCurrentCapacity( reading ) );

transaction.exec();
transaction.close();
}

private Double getCurrentCapacity( MeterReading reading ) {
return reading.getWhGenerated() - reading.getWhUsed();
}
}

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